The genome sequence of Streptomyces ambofaciens, a species known to produce the congocidine and spiramycin antibiotics, has revealed the presence of numerous gene clusters predicted to be involved in the biosynthesis of secondary metabolites. Among them, the type II polyketide synthase-encoding alp cluster was shown to be responsible for the biosynthesis of a compound with antibacterial activity. Here, by means of a deregulation approach, we gained access to workable amounts of the antibiotics for structure elucidation. These compounds, previously designated as alpomycin, were shown to be known members of kinamycin family of antibiotics. Indeed, a mutant lacking AlpW, a member of the TetR regulator family, was shown to constitutively produce kinamycins. Comparative transcriptional analyses showed that expression of alpV, the essential regulator gene required for activation of the biosynthetic genes, is strongly maintained during the stationary growth phase in the alpW mutant, a stage at which alpV transcripts and thereby transcripts of the biosynthetic genes normally drop off. Recombinant AlpW displayed DNA binding activity toward specific motifs in the promoter region of its own gene and that of alpV and alpZ. These recognition sequences are also targets for AlpZ, the ␥-butyrolactone-like receptor involved in the regulation of the alp cluster. However, unlike that of AlpZ, the AlpW DNA-binding ability seemed to be insensitive to the signaling molecules controlling antibiotic biosynthesis. Together, the results presented in this study reveal S. ambofaciens to be a new producer of kinamycins and AlpW to be a key late repressor of the cellular control of kinamycin biosynthesis.Streptomycetes are filamentous, soil-dwelling bacteria that undergo a complex morphological differentiation correlated with a rich biochemical specialization occurring during the late stages of growth. These prokaryotes are known for their capacity to biosynthesize a vast array of important secondary metabolites used in human activities, including antibiotics, antitumor agents, immunosuppressants, antihelmenthics, and herbicides. In spite of decades of genetic studies and industrial uses, members of the genus Streptomyces have recently revealed, by means of genomic analyses, their hitherto unsuspected ability to produce further novel secondary metabolites with potentially useful activities (5, 22, 37).In Streptomyces ambofaciens ATCC 23877, which was previously known to produce only the antibiotics congocidine (12) and spiramycin (42), the sequencing of the terminal regions of the linear chromosome (over circa 3 Mb; accession no. AM238663 and AM238664, respectively, for the left and right arms) has unveiled 14 novel secondary metabolite gene clusters (http://www.weblgm.scbiol.uhp-nancy.fr/ambofaciens/) (10). Among them, two clusters were experimentally shown to be involved in the biosynthesis of the siderophore coelichelin (3) and the pyrrole-amide congocidine (23), respectively. In our groups, the function of the duplicated type II polyketi...